#!/usr/bin/perl
# prints a region from a binary or text file (from position s of length l)
use strict;
use warnings;
use Getopt::Long;

sub usage {
  print "usage: $0 [-s <pos>] [-l len] <file>\n";
  exit(-1);
}

our $start=0;
our $len = "";
our $help;

usage unless GetOptions("start=i"          => \$start,
                        "len=i"            => \$len,
                        "help"             => \$help);
usage if $help;
local $/;  # slurp mode
my $data;
if (@ARGV) { 
  my $file = shift @ARGV;
  open FILE, "<$file" or die "can't open $file: $!";
  $data = <FILE>;
} else {
  $data = <STDIN>;
}
$len = length($data) unless $len;
print substr($data,$start,$len);